Dual-Responsive Polyacrylamide Microspheres with Migration Swelling Plugging Time Window for Profile Control in Harsh Reservoirs

To overcome the limitations of conventional profile-control and water-plugging agents in high-temperature and high-salinity reservoirs, such as poor thermal/salt resistance and uncontrollable plugging timing, temperature salinity dual-responsive polyacrylamide microspheres (PNMA) were designed and synthesized. They were prepared via ternary copolymerization using N-isopropylacrylamide, methacrylic acid, and a quaternary ammonium salt monomer, with a core–shell structure and amino-ester functionalization. Experimental results showed PNMA swelled from 83 to 573 nm in pure water at 80 °C, following a typical S-shaped curve. The logistic kinetic model accurately fitted this behavior, revealing that elevated temperature accelerates swelling kinetics. The modified Flory–Rehner equation well described equilibrium swelling factors at different salinities, confirming the low-salinity swelling and high-salinity contraction mechanism. A migration swelling plugging time window predicted 5 ∼ 7 days of effective plugging at 70 °C and 3000 mg/L salinity, consistent with experiments. Interfacial adsorption tests and molecular dynamics simulations showed amino-ester groups enhanced rock–surface interactions, boosting adsorption by 40% vs traditional PAM. In two-permeability core flooding, 4000 mg/L PNMA reduced high-permeability layer by 82% and raised low-permeability recovery from 35 to 62% (total +17.5%). This work establishes an innovation chain, offering a new water control and oil stabilization paradigm for complex reservoirs.